Engine mods

There's two main schools of thought on modifying an engine especially when it comes to old bike..  I don't subscribe to either.  I'll break down the two schools and tell you where I stand

School 1:  Keep it original

These are the guys that figure the original engineers knew best and it's best not to mess with their design.  These guys will work very hard to get everything back to the way it was when the bike was first made.  Any changes to the motor setup are fairly minimal and usually hidden.

The big advantage here is reliability.  Most often, making a bunch a changes to a motor to get more performance means sacrificing some reliability.  By keeping things stock, the motor is keep within its intended operating range and as such can be expected to last longer.

The downside is, if it was an underwhelming motor to begin with, it will be an underwhelming motor still.

School 2: Throw the catalog at it

These guys will put literally hundreds or thousands of dollars into a motor cramming into it every conceivable option available.  Bored, stroked, ported, high compression piston, custom carbs, if they can get it they'll stuff it done.

If they're lucky, and they know what their doing, they MIGHT get a good running motor out of the deal.  It takes ALOT of time and patience because everything has to be balanced, tuned, adjusted to get the motor running properly.  This can be costly and difficult to do, but it can make for an impressive end product.

For me, if I really wanted a big powerful engine why was I even messing with an XS650?  If I'm going to spend all that money to try and get big bike performance out of my little 650, I should just go buy a newer, bigger motor.  On the other hand, a stocker just didn't get me very excited.  So I made up chose to split the difference.

For my XS650 project, I ended up with the following modifications:

• Engined bored from 650cc to 680cc - doing this meant I could get a bit more performance without putting in new sleeves, MikesXS sells 6th over pistons that drop right in
• Aftermarket exhaust - nothing fancy, just some decent peashooters that look the part of a cafe bike
• Pod air filters - these dropped right in and did not require alot of tinkering with the carbs

The end result is a motor that looks cool, will run strong and better than stock, but was not so crazy to put together that I need hours and hours of tinkering to get it right.  I also kept the costs pretty reasonable along the way.